The Oak Brook, Ill.-based fast-food giant said sales at U.S. stores open at least 13 months fell 4.6% in November -- a drop that followed a 1% decline a month earlier.

"Today's consumers increasingly demand more choice, convenience and value in their dining-out experience," McDonald's Chief Executive Don Thompson said. "We are working to bring the McDonald's 'experience of the future' to life for our customers to better deliver against these evolving expectations.”

As part of that effort, McDonald’s wants to emulate fast-casual competitors such as Chipotle, which allow customers to customize their orders.

McDonald’s currently allows customers at several Southern California stores to customize its iconic hamburgers by placing the patty on a toasted artisan roll or adding items such as guacamole and applewood smoked bacon.